60 lines
1.5 KiB
Go
60 lines
1.5 KiB
Go
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package discover
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import (
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"bytes"
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"encoding/json"
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"errors"
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"fmt"
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"net"
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"os"
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"time"
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"git.faercol.me/faercol/http-boot-config/config/config"
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)
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var ErrNoServer = errors.New("no server found")
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var discoveryMsg = []byte("BOOT_DISCOVER")
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type discoveryPayload struct {
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ManagementAddress string `json:"managementAddress"`
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Version string `json:"version"`
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}
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func DiscoverServer(conf config.Autodiscovery) (string, error) {
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raddr, err := net.ResolveUDPAddr("udp", conf.DiscoveryAddr)
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if err != nil {
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return "", fmt.Errorf("invalid discovery address: %w", err)
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}
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conn, err := net.ListenUDP("udp", nil)
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if err != nil {
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return "", fmt.Errorf("failed to dial UDP multicast group: %w", err)
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}
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defer conn.Close()
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n, err := conn.WriteToUDP(discoveryMsg, raddr)
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if err != nil {
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return "", fmt.Errorf("failed to write to UDP connection: %w", err)
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}
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if n < len(discoveryMsg) {
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return "", fmt.Errorf("failed to write the entire message (%d/%d)", n, len(discoveryMsg))
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}
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conn.SetReadDeadline(time.Now().Add(conf.Timeout))
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resp := make([]byte, 2048)
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if _, err := conn.Read(resp); err != nil {
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if errors.Is(err, os.ErrDeadlineExceeded) {
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return "", ErrNoServer
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}
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return "", fmt.Errorf("failed to read response from server: %w", err)
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}
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var payload discoveryPayload
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if err := json.Unmarshal(bytes.Trim(resp, "\x00"), &payload); err != nil {
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return "", fmt.Errorf("failed to parse response from server: %w", err)
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}
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return payload.ManagementAddress, nil
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}
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